In a typical prior-art security installation one or more security sensors are provided locally about an environment to be secured. The security sensors are responsive to such specific events as an unauthorized intrusion and smoke and/or heat to provide a signal indication of the occurence of the event. The signal is applied to an alarm means, and often indicated at a control and alarm center over a communication link. The remote center may be a police station or a central, often computerized, control unit. The communication link usually is in the form of electrical wires or, less often, some other telecommunications channel.
The functional integrity of the security installation is a condition precedent to the provision of effective countermeasures intended to circumvent or ameliorate the threat. Without an adequate notice of the occurring of the environmental event it is impossible to take responsible action to preserve life or property.